In recent years, from the viewpoints of energy saving, resource saving, environmental load reduction and the like, there have been broadly utilized hot melt viscous adhesives; and as base polymers for the hot melt viscous adhesives, there are broadly used vinyl aromatic monomer-conjugated diene monomer-based block copolymers (for example, SBS; styrene-butadiene-styrene block copolymers and the like). Adhesive compositions obtained by using these block copolymers, however, are insufficient in the balance among retentivity, tack and tack strength, and these have been desired to be improved.
As their improving methods, for example, Patent Literature 1 discloses an adhesive composition composed of a triblock copolymer and a diblock copolymer. Further, Patent Literature 2 discloses an adhesive composition composed of a block copolymer obtained by coupling with a specific bifunctional coupling agent (specific dihalogen compound).
Further, Patent Literature 3 discloses an adhesive composition composed of a block copolymer obtained by hydrogenating, in a specific proportion, a block copolymer of a vinyl aromatic monomer and a conjugated diene monomer.